It's from Adventure Time:
We'll work together and use that serum you made. The one that was "Ah! So Spice!" And spice-bomb him non-stop 'till his butt falls out! How's that sound?
To make it clear, they're just pranking the guy to irritate him and make him go away.
What does this phrase mean, both literally and idiomatically?
I know that hair or teeth can fall out, but I can't picture a butt fall out.
Or does fall out mean leave here as in:
It's late, George. I have to fall out.